In general, a manual transmission needs to be operated by a driver in accordance with a road condition or a traveling speed. The manual transmissions are classified into a selective gear type manual transmission configured such that gear teeth of a gear shift stage selected by an operation of a shift lever mesh with one another, and an always meshing type manual transmission configured such that a gear on a main shaft and a gear of an auxiliary shaft always mesh with each other. In addition, a dual clutch transmission (DCT) allows a gear shift operation to be automatically performed through an operation of a gear actuator and an operation of a clutch actuator, and the dual clutch transmission has an advantage in that efficiency is high and the gear shift operation is quickly performed.
However, in the case of a rear wheel manual transmission or the dual clutch transmission (DCT) in the related art, a housing is supported at two or three points. For this reason, a degree of sagging of a shaft in the transmission is increased, which causes deterioration in durability and an increase in noise.